Manufacture of tungsten alloys low in tin and arsenic



Patented Mar. 19, 1929.

UNITED'VSTATE'S PATENT OFFICE.

FREDERICK M. BECKET, OF NEW YORK, N. Y., ASSIGNOR T ELECTED METALLURGICAL COMPANY, A. CORPORATION OF WEST VIRGINIA.

MANUFACTURE or 'rnNesrEN ALLOYS LOW IN 'rm AND ARSEN-IC;

No Drawing.

I The invention relates to the treatment of tungsten ores for the recovery of their tungsten content.

The'common tungsten ores carry the ele- 5 ment in the form of tungstates' For; ex-

ample, ferberite may be regarded as an iron tungstate, wolframite as an 1ron and manganese tungstate, and scheelite as a calcium tungstate. Such ores can be reduced without the tungsten present recovered as an alloy. It is the general practice to recover the tungsten as an alloy with iron since the melting point is lowered as the content of iron mcreases, and the iron is unobjectlonable where the tungsten is ultimately to form part of a ferrous alloy. The tungsten ore itself often contains suflicient iron to produce a suitable allo with the tungsten.

ungsten ores in general, however, carry other impurities which are objectionable unless separated from the tungsten. Among such impurities are tin and arsenic, and these are practically always present. Since the 25 tungsten content of high-speed steels is usually between and it will be evident that the ratio of tin to tungsten or of arsemc to tungsten must bevery low in the alloy which is incorporated in making such steels.

The invention is a process. for the manufacture of alloys low in tin and arsenic. from tungsten ores contaminated with these ele ments or either of them. I

I have discovered that if tungsten ores are reduced by an excess of silicon or silicon alloy. or if tungsten and silicon are reduced in the same charge, so that the alloy produced has a considerable content of silicon, a part only of the tin present will enter the alloy. The

tion of the total tin in the charge which enters the alloy recovered, appears to diminish progressively as the Silicon content of the alloy increases. The elimination of arsenic occurs in similar fashion. The percentage of silicon which it will be necessary to incorporate into the alloy will depend on the degree of contamination of the ore and on the specifications for tin and arsenic in the ferrotungsten special difficulty in the electric furnace, andrecovery of tin, by which is meant the propor- 1 Application filed December 11, 1926. Serial No. 154,307.

produced, but in many cases a silicon content between 10% and 35% is advantageous.

' Somewhat lower percentages of silicon are effective under some conditions. A silicon content in excess of 20% is usually preferred. The presence of the silicon lowers the melting point of the alloy and facilitates tapping. The furnace charge for producing the ferrotungsten-silicon contains the tungsten ore and silicon (preferably in the form of high-silicon ferro alloy) to reduce the ore and furnish the requisite excess of silicon, The silicon may be replaced, in whole or in part, by quantities of silica and carbon equivalent thereto. The silica in the ore is of course available for reduction to silicon, and lowgrade ores can be employed and their silica content utilized for this purpose.

Ferrotungsten-silicon as such is not a suitable material for addition to ferrous alloys such as high-speed steel since its silicon con- 7 tent is too high. In accordance with the preferred embodiment of my invention, the alloy low in tin and arsenic prepared as-described above is therefore treated to oxidize the excess of silicon. A metal oxide is preferably .7 used for this oxidation and as a result. the metal of the oxide enters the alloy. An oxide of any metal which is not detrimental to the alloy may be used, but an oxidized tungsten compound such as one of the common tungsten minerals is preferably used. A further uantity of tungsten is thereby added to the errotungsten.

Where a tungsten ore is used in the second stage of the process it may likewise be one 35 which is contaminated with tin and arsenic. This is because there is an elimination of these elements in the second stage as well as the first, and also because any impurities which enter in the second stage are diluted by the high grade alloy produced in the first stage. Exclusion of tin and arsenic is not as effective in the second stage as in the first, however, and it is desirable to use an ore low in the impurities in question in the second stage. My invention contemplates a twostage process in which the available ore which is most contaminated with tin and arsenic.

' Pounds.

. Wolframite 15,612 Quartzite 7,806 Carbon (coke, coal and charcoal) 7 ,462 Fluorspar 200 h Sn The recovery of tungsten as ferrotungstensilicon was 93.15%. alloy produced analyzed as follows:

Wolfram- Ferromagite stem-silicon Per cent. Per cent. W 53.05 56. 39 F 10. 34 11. 47 Mn 8.05 6. 92 Si 18. 74 AS 1. 36' 0. 23 0. 17 0. 022

Over 80% of tin and a like proportion of the arsenic were eliminated.

The ferrotungsten-silicon thus produced was used to reduceamixture of 7000 lbs. of wolframite which had been magnetically treated for elimination of tin, and 6500 lbs. of scheelite. The analyses of the ores and the final alloy are as follows:

Wolfram- Ferrotung- Seheelite 8 Stan Per cent. Per cent 56. 87 80. 98 11. 02

The overall recovery of tungsten in the entire process was approximately 90%.

The following additional example of the production of ferrotungsten-silicon shows the influence of a higher content of silicon in excluding tin. The ore was a wolframite contalnlng: Per cent. W 53.39 Fe 13.07

The wolframite and the The furnace charge contained ore, quartzite and carbon. The alloy produced contained:

Percent.

Sn .s 0.04

I claim:

1. Process of making tungsten alloys low in tin and arsenic fromores contaminated with these elements which comprises reducing the ore, alloying silicon with the tungsten as reduced to produce an alloy containing at least 10% of silicon, and then oxidizing the major portion of the silicon content with a metal oxide in which the ratio of the total reducible metals to the total tin and arsenic is higher than in the ore first reduced.

2. Process of making tungsten alloys low in tin and arsenic from ores contaminated with these elements which comprises reducing the ore, alloying silicon with the tungsten as reduced to produce an alloy containing at least 10% of silicon, and then oxidizing the major portion of the silicon content with a tungsten ore in which the ratio of the total reducible metals to the total tin and arsenic is higher than in the ore first reduced.

3. Process of making tungsten alloys low in tin and arsenic from ores contaminated with these elements which comprises reducing the ore, alloying silicon with the tungsten as reduced to produce an alloy containing at least 10% of silicon, and-then oxidizing the major portion of the silicon content with a tungsten ore lower in tin and arsenic than that first referred to.

4. Process which comprises smelting a tungsten-containing material contaminated with tin and arsenic, incorporating at least 10% of silicon into the reduction product, and then desiliconizing'the reduction product with a metal oxide in which the ratio of total reducible metals to the total tin and arsenicis higher than in the material first smelted.

5. Process which comprises smelting a tungsten-containing material contaminated with tin and arsenic, incorporating at least 10% of silicon into the reduction product, and then desiliconizing the reduction product with a tungsten ore in which the ratio of total reducible metals to the total tin and arsenic is higher than in the material first smelted.

In testimony whereof, I aflix my signature.

FREDERICK M! BECKET. 

